PC won't power up. Boot device LED

[Newt]

Hi all
Recently I helped my friend build a system, he doesn't live anywhere near me so it was pretty difficult. Last night he decided to reapply his thermal paste as he was getting some bad temps. In doing this he removed the CPU to clean it and also one stick of RAM. Now the PC won't start up correctly. When powered on, the device gets stuck at a point and displays the red Boot Device LED. From here nothing else happens. I've told him to try all the usual unplug and plug back in but I’m not sure what to do next.

Help me!

Specs of the offending PC:

Asus P8Z68-V PRO Z68 Socket 1155 8 Channel HD Audio ATX Motherboard
Intel Core i5 2500K 3.3GHz Socket 1155 6MB Cache Retail Boxed Processor
Samsung HD103SJ Spinpoint F3 1TB Hard Drive SATAII 7200rpm 32MB Cache - OEM
Arctic Cooling Freezer 7 Pro rev 2 Socket 775, 1156, 1155, 1366, AM2, AM3 Heatpipe CPU Cooler
Asus GTX 560 DCII OC 1GB GDDR5 Dual DVI Mini HDMI PCI-E Graphics Card
LiteOn iHAS224 24x DVD±RW DL RAM & Lightscribe SATA Optical Drive - OEM Black
Skill 8GB (2x4GB) DDR3 1600Mhz RipjawsX Memory Kit CL9 (9-9-9-24) 1.5V

[3DWizard]

So he received a red LED when he tried to boot up? Tell him to remove all power cables throughout the PC and tighlty connect them all again, making sure none are loose. Same with components, he has probably knocked something when playing with it.

[Newt]

He has removed, replaced and checked all the cables a number of times to no avail. Any other ideas?

[Pilgrim_uk]

In doing this he removed the CPU to clean it and also one stick of RAM

If this is the only thing he has done and it worked before. Reseat the CPU then switch it back on. Remove the stick of memory he did before restart. Remove all memory and see if he gets the normal beeps for that mobo.

[Ginger-Menace]

if you didnt do any over clocking a simple cmos reset might do the trick

[BlauLicht]

if its anything like this its a faulty mobo nd not cpu i didnt realise at the time of uploading the vid but as soon as i rma the mobo nd got a new one the pc worked fine